dracut-kdump.sh: simplify dump_ssh
    
    upstream: fedora
    resolves: bz2003832
    conflict: none
    
    commit 7a9823b42e13cb9ff535009f28f89d197b14bbb0
    Author: Kairui Song <kasong@redhat.com>
    Date:   Tue Aug 3 13:23:26 2021 +0800
    
        dracut-kdump.sh: simplify dump_ssh
    
        There is a workaround for `scp` that it expects IPv6 address to be
        quoted with [ ... ], only apply the workaround once and store the
        updated `scp` address to reuse it.
    
        Signed-off-by: Kairui Song <kasong@redhat.com>
        Acked-by: Philipp Rudo <prudo@redhat.com>
    
    Signed-off-by: Tao Liu <ltao@redhat.com>